[CUDA] Add -fcuda-flush-denormals-to-zero.

Summary:
Setting this flag causes all functions are annotated with the
"nvvm-f32ftz" = "true" attribute.

In addition, we annotate the module with "nvvm-reflect-ftz" set
to 0 or 1, depending on whether -cuda-flush-denormals-to-zero is set.
This is read by the NVVMReflect pass.

Reviewers: tra, rnk

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D18671

llvm-svn: 265435

1 files changed, 8 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 11f5bea64ca..f525246e6ef 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -472,6 +472,14 @@ void CodeGenModule::Release() {
     getModule().addModuleFlag(llvm::Module::Override, "Cross-DSO CFI", 1);
   }
 
+  if (LangOpts.CUDAIsDevice && getTarget().getTriple().isNVPTX()) {
+    // Indicate whether __nvvm_reflect should be configured to flush denormal
+    // floating point values to 0.  (This corresponds to its "__CUDA_FTZ"
+    // property.)
+    getModule().addModuleFlag(llvm::Module::Override, "nvvm-reflect-ftz",
+                              LangOpts.CUDADeviceFlushDenormalsToZero ? 1 : 0);
+  }
+
   if (uint32_t PLevel = Context.getLangOpts().PICLevel) {
     llvm::PICLevel::Level PL = llvm::PICLevel::Default;
     switch (PLevel) {